The present invention relates to a method of operating a cooling and heating circuit of a motor vehicle.
Known cooling and heating devices of motor vehicles with an internal combustion engine include as a rule a cooling and heating circuit with several cooling medium paths, for distribution and withdrawal when needed of heat which is generated in the internal combustion engine, and additional aggregates, for example turbochargers, transmissions, and generators, in the sense of a thermal management. Operational and environmental parameters, such as for example the temperatures and/or the pressure conditions of the media, the rotary speed, the load and the temperature of the internal combustion engine, the components and aggregates, as well as the temperature of the surrounding air and the passenger space, are detected in an electronic control unit as input signals and processed to provide output signals. The output signals are used for controlling of the majority of the electrically operated feeding and adjusting devices.
Such a cooling device is disclosed for example in the European patent document EP 0 499 071 A1. It includes a cooling medium circuit for cooling the internal combustion engine. Furthermore, the machine oil and the load air are cooled with air by additional oil cooler and charge air cooler with air. A control device which has as least one microprocessor determines, depending on a plurality of measured status variables, the cooling power demand or heat demand of each individual aggregate or component of the cooling system and regulates the cooling medium flows individually, but with consideration of the requirements of the total system.
For controlling the material and heat flows, electrically controlled pumps and valves are provided. Furthermore, additional regulatable heating devices are connected to the cooling device, for example for warming up of the vehicle space or the wiping water of windshield wiper device, so that excessive heat energy can be used for heating when needed.
The cooling medium circuit for cooling of the internal combustion engine shown in FIG. 6 of the European patent document EP 0 499 071 A1 has a first cooling medium path through a bypass conduit, a second cooling medium path through a main cooler of the internal combustion engine, a third cooling medium path through a heating heat exchanger and a fourth cooling medium path through a heat accumulator.
During a cold start the cooling medium flows so as to bypass the main cooler and through the bypass conduit both to the internal combustion engine back, and supplies it in a lower region, namely in the region of the cylinder block. This small circuit provides low cooling power, so that the internal combustion engine can reach fast its operational temperature and the fuel consumption is advantageously reduce. When the cooling medium temperature increases, a valve opens the second cooling medium path to the main cooler, which when needed cooperates with a shutter and a blower and draws the excessive heat of the cooling medium. In a third cooling medium path a heating heat exchanger is arranged, through which a part of the cooling medium flow is supplied when needed, to heat the passenger space.
When the cooling power of the heating heat exchanger is sufficient, the cooling medium path with the main cooler can be completely blocked. The excessive heat is supplied in this operational condition exclusively in the passenger space, which at low outside temperatures improves the comfort. During the warming up phase of the internal combustion engine as a rule the heat produced during combustion is used for reaching the operational temperature of the internal combustion engine fast, to lower the fuel consumption and to reduce the emission of damaging substances. The cooling medium which flows through the heating heat exchanger is significantly reduced or completely blocked, so that during this period costs of the comfort involve only a small or no energy for heating of the passenger space.
The heat accumulator which can be formed as a latent heat accumulator can store waste heat generated by the fuel combustion in a normal operation, and gives out the stored heat when necessary for warming up the internal combustion engine, in particular with low environmental temperatures for fast warming up and can also heat the passenger space. It is provided with valve means and controlled by the control unit so that it can be operated in series with the heating heat exchanger or parallel to it and can supply the heat when needed to the cooling medium or withdraw the excessive heat.
A cooling and heating circuit with a latten heat accumulator is also disclosed in the German patent document DE 196 01 319 A1. The cooling medium flow through the heat accumulator is also regulated by a control unit which evaluates signals of temperature sensors arranged on the internal combustion engine and on the heat accumulator and detects the temperature of the cooling medium as well as of special components. In addition to the desired heat introduction in the starting phase of the internal combustion engine, the heat accumulator improves the efficiency of the internal combustion engine in a partial load region, when the temperature of the cooling medium increases above the mainly used value 95° to a value 105° C. For avoiding an overheating of the internal combustion engine, the temperature of the cooling medium can be however lowered again in full load operation. Known heat accumulators due to their thermal inertia, significantly slow this process, which can lead to damages of components of the internal combustion engine. In order to achieve a fast change of the cooling temperature, special devices are needed in the cooling circuit.
German patent document DE 37 38 412 A1 further discloses a device and a method for regulation of the temperature of an internal combustion engine. The cooling medium circulates in a cooling circuit which is composed of several cooling medium paths. A first cooling medium path leads to a bypass conduit, a second cooling medium path leads to a main cooler of the internal combustion engine, and a third cooling medium path leads to a heating heat exchanger which serves for climatization of a passenger space. The cooling medium distribution is performed by electrically actuated valves at the branches of the cooling medium path. In addition, a mechanically or electrically driven pump is arranged in the cooling circuit. For controlling the valves and the electrical pump, a control unit is provided which supplies operational and environmental parameters of the internal combustion engine as input signals, such as for example the rotary speed and the temperature of the internal combustion engine, the pressure and the temperature of the cooling medium, and also the temperature of the environmental air and the passenger space. The control unit processes these informations to provide output signals which form adjusting variables for the control valves and the electric pump.